第九篇 IO流技术（九）

打印流

package com.zzp.demo;

import java.awt.image.FilteredImageSource;
import java.io.BufferedOutputStream;
import java.io.FileDescriptor;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.PrintStream;

/**
 * 
 * PrintStream
 * @author java
 *
 */
public class PrintTest01 {
    public static void main(String[] args) throws FileNotFoundException {
        PrintStream ps = System.out;
        ps.print("生活不易");
        ps.println("且行且珍惜");
        
        //加上true之后，自动刷新
        ps = new PrintStream(new BufferedOutputStream(new FileOutputStream("4.txt")),true);
        ps.print("生活不易");
        ps.println("且行且珍惜");
        ps.println("真是这么简单");
        ps.close();
        
        //重定向输出端
        System.setOut(ps);
        System.out.println("重定向");
        
        //重定向回控制台
        System.setOut(new PrintStream(new BufferedOutputStream(new FileOutputStream(FileDescriptor.out)),true));
        System.out.println("重定向回控制台");
    }
}

 PrintWriter

package com.zzp.demo;

import java.awt.image.FilteredImageSource;
import java.io.BufferedOutputStream;
import java.io.FileDescriptor;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.PrintStream;
import java.io.PrintWriter;

/**
 * 
 * PrintWriter
 * @author java
 *
 */
public class PrintTest02 {
    public static void main(String[] args) throws FileNotFoundException {
        //加上true之后，自动刷新
        PrintWriter pw = new PrintWriter(new BufferedOutputStream(new FileOutputStream("4.txt")),true);
        pw.print("生活不易");
        pw.println("且行且珍惜");
        pw.println("真是这么简单");
        pw.close();
    }
}

 随机读取流 RandomAccessFile

package com.zzp.demo;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;

/**
 * 
 * 随机读取流 RandomAccessFile
 * 
 * @author java
 *
 */
public class RandTest01 {

    public static void main(String[] args) throws IOException {
        //分多少块
        File src = new File("src/com/zzp/demo/CopyTxt.java");
        //总长度
        long len = src.length();
        //每块的大小
        int blockSize = 1024;
        //多少块，不够整数的向上取整
        int size =(int) Math.ceil(len*1.0/blockSize);
        System.out.println(size);
        
        //起始位置
        int beginPos = 0;
        //实际大小
        int actualSize = (int)(blockSize > len?len:blockSize);
        for(int i=0;i<size;i++){
            beginPos = i*blockSize;
            if(i==size-1){//最后一块
                actualSize = (int)len;
            }else{
                actualSize = blockSize;
                len -= actualSize;
            }
            split(i,beginPos,actualSize);
        }
    }
    
    //指定起始位置，读取剩余的所有内容
    public static void test01(){
        try {
            RandomAccessFile raf = new RandomAccessFile(new File("src/com/zzp/demo/CopyTxt.java"), "r");
            //随机读取的位置
            raf.seek(2);
            // 3、操作（写入操作）
            byte[] flush = new byte[1024]; // 1k一读取
            int len = -1;// 设置默认长度为-1
            while ((len = raf.read(flush)) != -1) {
                System.out.println(new String(flush, 0, len));
            }
            raf.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    //分块思想
    public static void test02(){
        try {
            RandomAccessFile raf = new RandomAccessFile(new File("src/com/zzp/demo/CopyTxt.java"), "r");
            //起始位置
            int beginPos = 2;
            //实际大小
            int actualSize = 1026;
            //随机读取的位置
            raf.seek(beginPos);
            // 3、操作（写入操作）
            byte[] flush = new byte[1024]; // 1k一读取
            int len = -1;// 设置默认长度为-1
            while ((len = raf.read(flush)) != -1) {
                if(actualSize > len){
                    System.out.println(new String(flush, 0, len));
                    actualSize -= len;
                }else{
                    System.out.println(new String(flush, 0, actualSize));
                    break;
                }
            }
            raf.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    /**
     * 指定第i块的起始位置 和实际长度
     * @param i
     * @param beginPos
     * @param actualSize
     * @throws IOException
     */
    public static void split(int i,int beginPos,int actualSize ) throws IOException {
        RandomAccessFile raf =new RandomAccessFile(new File("src/com/sxt/io/Copy.java"),"r");
        //随机读取 
        raf.seek(beginPos);
        //读取
        //3、操作 (分段读取)
        byte[] flush = new byte[1024]; //缓冲容器
        int len = -1; //接收长度
        while((len=raf.read(flush))!=-1) {            
            if(actualSize>len) { //获取本次读取的所有内容
                System.out.println(new String(flush,0,len));
                actualSize -=len;
            }else { 
                System.out.println(new String(flush,0,actualSize));
                break;
            }
        }            
        
        raf.close();
    }
}